While, however, the constitution of individual eyes acknowledges one color more pleasing than another, there is none, perhaps, which does not prefer the coldest monochromatic to entire absence of color, as in blank white, or to an absolute vacancy of light, as in black. Sepia pieces are more agreeable than the neatest drawings in China ink, or the most graceful curves done in chalk upon a blackboard. But however the eye may admire a severe and simple unity, it relishes still more a harmonious complexity; and a very mediocre little _pensee_ in water colors, will prove more generally attractive than the monochromatic copies in the Liber Veritatis. But to this complexity there must be limits--an endless and incongruous variety teases and revolts; the discordant effect of innumerable tints, among which some are sure to be uncongenial to each other, is always extremely irritating. There ought, then, to be a scale of color, it would seem, within whose limits the purest harmonies are to be found, and beyond which subdivisions should be no more allowed than in constant musical notes. When this idea strikes, as it must have, many artists, reason, consideration, instinct, and all, refer at once to the solar spectrum as such an one. The analogy between this scale, which governs the chromatics of the sunset and thunderstorm, and that which the science of man has established, empirically, for harmonies, is remarkable, and we shall try to make it patent. They are both scales of seven: the tonic, mediant, and dominant, find their types in red, yellow, and blue, while the modifications on which the diatonic scale is constructed, resemble, numerically and esthetically, the well-known variations in the spectrum. The theory of harmonies in optics is the same as in acoustics, the same as in everything--it is based on simplicity. Those colors, like those notes, the number of whose vibrations or waves in the same time bear some simple ratio to each other, are harmonious; an absolute equality produces unison; and a group of harmonies is melody both in music and in color. At this point we cannot but hint at the analogy already discovered between the elements of music and the elements of form. Angles harmonize in simple analysis, or intricate synthesis, whose circular ratios are simple.